In the following, the field of common rail injection technology will be outlined briefly as a particularly attractive field of use of the teachings herein. However, the invention can also be used in other technical fields in which efficient activation is useful.
Fuel injection devices for internal combustion engines are extensively known from automobile technology. High-pressure injection systems with accumulators, in which the fuel to be injected is accumulated at a pressure of many hundreds of bars and is led into combustion chambers via injection valves, have proven to be particularly efficient.
To operate such a high-pressure injection system, regulation of the pressure in the high-pressure accumulator, which usually in particular activates a high-pressure pump with a manipulated variable, is required. Additionally known from the literature are so-called pressure reduction valves, which are either integrated into individual injection valves (e.g. DE 101 11 293 A1) or are generally mentioned in the description of control systems for accumulator injection systems (e.g. DE 10 2007 059 116 A1). Also known from DE 10 2012 204 252 B3 is a pressure reduction valve which is integrated in an injection valve.
Such a pressure reduction valve is very useful for efficient regulation of the pressure in the accumulator, since the high-pressure pump can be used exclusively for the pressure build-up and since, in the event of changes in the reference variable, for example in the event of a change in the operation of the internal combustion engine, a fast pressure reduction is occasionally necessary but is not expediently possible via the injection valves alone. The consequence would be so-called hard combustion, which is not desired during operation of the internal combustion engine.
In order to permit an efficient pressure reduction in this way, it is known in such a control system also to provide a magnetically controlled pressure reduction valve which can be activated electrically. When activating such a valve, it is important that the volume of liquid let through can be controlled accurately, in that the valve can be opened and closed in a very well defined manner. This is usually achieved in that very fast opening and closing are achievable by means of an electromagnetic drive, so that the valve can virtually be switched digitally between an opened and a closed position, so that only the time period of the opening decides on the volume of liquid let through. Such a drive leads in turn to high acceleration values of the mechanical parts of the valve, i.e. in particular a closure element which opens and closes a valve opening. Such a high acceleration in turn firstly generates noises, which can be annoying, and wear in the area of the sealing faces.